This proposal is designed to test the hypothesis that braces used for the treatment of Legg-Calve-Perthes' Disease (LCPD) do not substantially alter the stress distribution within the diseased but undeformed femoral head. While bracing is the most commonly used treatment for LCPD, there is little firm clinical evidence, and virtually no experimental evidence, to confirm the long term efficacy of braces. Clinical evidence of efficacy is difficult to produce since the deleterious effects of LCPD are often not apparent for many (20 to 40) years and since scientifically sound long term follow-up studies are difficult to carry out. Until recently, methods did not exist to study the three-dimensional effects of bracing on the stress distribution throughout the femoral head during activities of daily living. The investigators in this grant have, for the first time, the multiple capabilities to study this problem in a comprehensive way. In order to determine the effects of bracing on the stress distribution throughout the femoral head in LCPD we will: (1) instrument a modular Atlanta Scottish Rite abduction brace to allow accurate determination of all external loads applied to the thigh by the device; (2) carry out kinematic, kinetic, and EMG analysis of normal children and patients with early LCPD in and out of the instrumented brace; (3) confirm our existing models (or develop new CT scan-based models) of bony architecture, surface contact, and muscle location; (4) calculate the three-dimensional muscle and joint forces during gait and determine the time-dependent joint contact geometry; and (5) apply the joint force and contact geometry throughout the gait cycle to newly developed three-dimensional linear elastic finite element models of the juvenile proximal femur to allow calculation of the stress distribution throughout the proximal femur in and out of braces.